This project is concerned with the development of statistical/mathematical methodology useful in the assessment of human health risks associated with exposures to potentially hazardous environmental agents. The primary focus is on the generation of improved statistical techniques for estimating adverse human health effects from laboratory animal data; and special emphasis is placed on dose-response modeling, low-dose extrapolation and extrapolation of toxicologic responses across species. Consideration is also given to the modeling of epidemiologic data in the risk assessment process. Present research efforts are concerned with the distribution of virtually safe dose level estimates under a two-stage model of carcinogenesis, with the estimation of working lifetime effects from continuous low-level exposures based on short-term occupational exposure data, with the impact of pharmacokinetic considerations on dose-response modeling in carcinogenesis, and with various methodological issues bearing on teratogenic risk assessment.